This invention relates generally to track-mounted, articulated overhead doors and particularly relates to an improved overhead door having an impact-resistant, knock-out bottom section.
Overhead doors having an articulated construction, such as those generally employed in garages, warehouses, or other enclosed structures, typically involve the use of a plurality of panels extending transversely across the door opening and arranged in a vertical linear array with adjacent edges of the panels flexibly coupled by means of hinges. This flexibility permits the door to be moved from a generally vertical orientation immediately adjacent the opening to an overhead horizontal position by means of a pair of parallel, curved tracks located on each side of the multi-sectioned door. The guide trackways generally include a vertical section which positions the door adjacent the opening, a horizontal section at the upper end of the vertical section that determines the open position of the door, and a curved section connecting the vertical and horizontal sections and over which the panels travel between the vertical and horizontal positions. The relative orientation of the door and the tracks is maintained by means of rollers coupled to the various sections of the door and positioned within and engaging the guide tracks. Each of the roller shafts is rigidly affixed to a section, or panel, of the door while the rotating portion of the roller which is mounted on the shaft engages the tracks, with its movement thereby constrained in guiding the door along the tracks.
While this type of door offers clear advantages in terms of ease of handling and storage in the open position, it has also suffered from various installation and operating limitations. The prior art discloses many approaches to solving design, construction and installation problems associated with these doors as evidenced by the following patents, and the improvements they represent, in this field: U.S. Pat. Nos. 2,907,383 to Kloote et al (plastic rollaway door for reduced weight and improved environmental durability); 2,938,578 to Stull (improved weather-tight door seal); 2,951,533 to Lucas et al (light-weight garage door assembly with interchangeable interlocking articulated sections); 3,023,804 to Howell (improved door lower seal and positioning means); 3,034,575 to Stroup (vertically acting door with improved seals); 3,090,427 to Stroup et al (upwardly acting door assembly with adjustable door jamb and sill seal positioning and locking means); 3,648,755 to Thiele (combination connecting cover/seal strip and hinge for inter-panel space of articulated doors); 3,654,730 to Fraleigh (flexible barrier extending across bottom portion of overhead door opening for intercepting debris); and 3,734,161 to Pierce (curtain-type overhead door with flexibly interlocking substantially flat panels which are rolled onto a barrel or drum).
Still another approach to a flexible partition for covering an opening is disclosed in U.S. Pat. No. 4,122,887 to Dussault et al which describes a pliant curtain closure supported by its upper edge and a portion of one side edge and which includes a window cut-out and attached weights to provide inertia when the closure is opened or when it is returned to its closed position.
Thus, it is readily apparent that the search for improvements in flexible, overhead doors has been rather extensive and intense. To date, however, the problem of damage to an overhead door caused by the impact of an object, such as a moving vehicle, with the door has not been addressed. An impact force applied to the lower section of the door when in the open or a partially closed position represents a constant potential source of damage thereto involving expensive repairs, temporary loss of the security and environmental protection provided by the door, and repair of the object, such as a forklift, automobile, or truck, impacting the overhead door. The present invention is directed to overcoming this problem and provides an improvement in articulated overhead doors which enhances their durability and safety.